Semi-Closed Pyrolysis System for Light Hydrocarbon Isotope Analysis
Solution Overview
Problem
Current methods for analyzing the carbon isotope composition of light hydrocarbon monomers in semi-closed pyrolysis systems are inefficient, as they require excessive dichloromethane, are laborious, and fail to effectively separate and enrich C5+ hydrocarbons, leading to errors in natural gas exploration.
Innovation Solution
A semi-closed pyrolysis system equipped with a liquid nitrogen freezing device is used to collect and enrich C5-C8 light hydrocarbons, allowing for the determination of their carbon isotope composition through a method involving vacuumization, pyrolysis, and gas chromatography analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the gold tube is immersed in dichloromethane for hydrocarbon collection, then all liquid hydrocarbons including light hydrocarbons can be collected, but the method requires excessive dichloromethane (over 50 ml per use), is laborious, and the gold tube cannot be reused
Solution Approach 1:
The patent employs phase transition of carbon dioxide from supercritical state to gas state for hydrocarbon extraction and enrichment. By controlling temperature and pressure, CO2 transitions between supercritical and gaseous phases, enabling efficient extraction of light hydrocarbons without requiring large volumes of dichloromethane, thus reducing chemical consumption and operational complexity
Solution Approach 2:
The patent utilizes parameter changes of CO2 by adjusting temperature and pressure to achieve different phases. The system maintains CO2 in supercritical state during extraction, then reduces pressure to convert it to gas phase for hydrocarbon enrichment, thereby eliminating the need for excessive dichloromethane and enabling gold tube reuse
2Measurement precision
If C1-C4 hydrocarbons and C5+ hydrocarbons are analyzed together by gas chromatography, then complete hydrocarbon analysis is achieved, but peak coalescence occurs for C1-C4 hydrocarbons due to their higher content (more than 2 orders of magnitude higher than C5+)
Solution Approach 1:
The patent segments the hydrocarbon analysis into two distinct parts: C1-C4 hydrocarbons and C5+ hydrocarbons. By using CO2 phase transition to separately enrich C5+ hydrocarbons and analyze them independently, the method avoids peak coalescence issues when analyzing all hydrocarbons together, thereby improving measurement precision without significantly increasing device complexity
Solution Approach 2:
The patent extracts C5+ hydrocarbons from the mixed hydrocarbon sample using supercritical CO2. By taking out the C5+ fraction for separate analysis, the method eliminates interference from abundant C1-C4 hydrocarbons, ensuring accurate detection of trace C5+ components without requiring complex analysis systems
3Reliability
If a closed system pyrolysis method is used, then light hydrocarbons can be prepared, but a small amount of crude oil and heavy hydrocarbon gas fail to be discharged and cracked, resulting in mixed pyrolysis liquid and residual hydrocarbons that differ from actual exploration conditions
Solution Approach 1:
The patent introduces supercritical CO2 as an intermediary medium in the pyrolysis system. CO2 facilitates the discharge and transport of pyrolysis products, ensuring complete removal of crude oil and heavy hydrocarbon gas. This intermediary作用 improves experimental reliability by better simulating actual exploration conditions without significantly increasing system complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables efficient enrichment and analysis of C5-C8 light hydrocarbons, reducing the need for additional devices and experiments, and improving the accuracy of geochemical research in natural gas exploration.
Implementation Method 1
adding liquid nitrogen into the liquid nitrogen storage container; opening a hydrocarbon discharge valve of the gas-liquid collector; successively opening the inlet valve and the outlet valve, so as to diffuse gas of the pyrolysis product into the collecting vessel with a capacity of 10 ml to enrich C5-C8 light hydrocarbons from the gas of the pyrolysis product
Implementation Method 2
placing a hydrocarbon source rock sample which has a weight not less than 50 g and a diameter of 3-10 mm into the semi-closed pyrolysis system for a pyrolysis experiment
Data Source
AI summary
A semi-closed pyrolysis system, including a liquid nitrogen freezing device, a gas-liquid collector and a pyrolysis gas collecting device. The liquid nitrogen freezing device includes a collecting vessel, a liquid nitrogen storage, an air inlet pipe, an air outlet pipe and a temperature detector. The collecting vessel is arranged in the liquid nitrogen storage container, and is provided with a stainless steel cap. The stainless steel cap is provided with three holes respectively for the air inlet pipe, the air outlet pipe and the temperature detector to pass through. The air inlet pipe and the air outlet pipe are each provided with a valve. The temperature detector includes a probe and a temperature sensor electrically connected with the probe. The probe extends into the collecting vessel. A method for determining carbon isotope composition of light hydrocarbon monomers based on such system is further provided.